When will we meet?

2/12/2010

I asked children to solve the following problem.

Let's say between Farmington and West Hartford is 10 miles. One person leaves Farmington and moves towards West Hartford. Another person goes from West Hartford towards Farmington. They both take the same road. The first person goes 4 miles per hour, the second 1 mile per hour. In how many hours will they meet?

I took toys and marked each mile with a toy on the floor. I asked 2 kids to volunteer . The first child stood at one end of the 'road': Farmington. The second child stood in another end: West Hartford. I asked kids where they would be in one hour. The first child stepped to the toy marking end of 4th mile. The second child moved to the toy marking end of 1st mile (from his side). Then I asked them where they would be in two hours. Kids met at 8th mile (for first child) and 2nd mile (for second child).
In how many hours will they meet? 2. Correct!

After that I changed distance and speeds calling different children and asking the same question: When will they meet?

After we were done I showed another way to solve similar problems.
I explained that in one hour both people will move 4 + 1 miles together. 4 + 1 = 5 miles. We have 10 miles total. How many times you need to take 5 miles to get to 10? 2. Correct!